1. Field of the Invention
The present invention concerns the field of microelectronics and in particular concerns a control unit to control a dual-energy tomosynthesis.
2. Description of the Prior Art
Contrast agent-assisted dual-energy tomosynthesis (CEDET) is a recently developed method in mammography. In such dual-energy imaging, low-energy images are initially acquired without application of contrast agent, and high-energy x-ray images are subsequently generated after a contrast agent injection. This is followed by a calculation method in which the high-energy x-ray images are subtracted with weighting from the low-energy x-ray images. The goal is to be able to better detect specific tissue structures (for example tumor tissue or micro-calcifications). The physical bases for a tomosynthesis method are described (among other things) by Bittner U., Düber C., Koch R., et al. in “Digital Multilayer Tomographie: A New Method of Implementing Classical Serioscopy”, Electromedica, 1989; 57:36. In tomosynthesis, a number of projection exposures are acquired from different angles or directions. A data volume of the subject to be examined (normally the female breast, but the present application is not limited to this usage) is subsequently reconstructed from the image data sets obtained in such a manner. The advantage of the method is that such tissue slices can be better acquired the deeper that they are located in the examination subject and/or the more that they are overlaid by denser tissue structures (for example fat tissue).
An improvement of the tomosynthesis method is apparent in contrast agent-assisted tomosynthesis. Before execution of the high-energy x-ray images of the patient, a contrast agent (normally iodine) is administered intravenously before the breast is irradiated. The high-energy acquisitions (which are normally obtained with an energy level above 33 kV) serve to cause visualization of the contrast agent enrichment in tissue and its progression over time. Malignant tumor tissue has a different contrast agent progression (enhancement) with respect to time than benign tissue; the presence of tumor tissue can be concluded based on the contrast agent presentation.
In digital dual-energy subtraction tomosynthesis, image data sets from a first, low-energy x-ray radioscopy are recombined with image data sets from a second, high-energy x-ray radioscopy (after contrast agent injection) in order to obtain a subtraction image. In the recombined subtraction exposure, the tissue in which the contrast agent has enriched in an intensified manner can be shown with emphasis.
This method basically assumes that the patient must be subjected to a double x-ray radioscopy during an examination (in which the breast is compressed and remains statically positioned): a radioscopy to acquire low-energy x-ray images (in order to be able to depict morphological structures of the examination subject), and a radioscopy to acquire high-energy x-ray images (in which the contrast agent enrichment can be shown). Since in this method the patient is exposed to a doubled radiation dose, there exists a basic need to minimize the radiation exposure for the patient as much as possible. Furthermore, it is significant to optimize the quality of the reconstructed image data in order to be able to ensure an improved sensitivity and specificity, so as to be able to ensure a better finding result.
In conventional CEDET methods, it is a disadvantage that the acquisition parameters cannot be configured to execute the second tomosynthesis scan with . high energy level. In particular, this second scan cannot be adapted to examination-specific and patient-specific conditions (such as breast density, tissue composition etc.) that can be derived from the image data of the first tomosynthesis scan. In the conventional methods, this disadvantage has led to suboptimal image results.